High-Strength Polylactic Acid (PLA) Biocomposites Reinforced by Epoxy-Modified Pine Fibers

Abstract

The stiffness and tensile strength of biopolymers (e.g., polylactic acid (PLA)) are less than desirable for load-bearing applications in their neat form. The use of natural fibers as reinforcements for composites (for large-scale three-dimensional (3D) printing) has expanded rapidly, attributable to their low weight, low cost, high stiffness, and renewable nature. Silane and acid/alkali are typically used to modify the surface of natural fibers to improve the fiber/polymer interfacial adhesion. In this study, a simple method of impregnation was developed to modify pine fibers (loblolly, mesh size of 90–180 μm, 30 wt %) with a solvent-borne epoxy to reinforce PLA. As a benefit of the epoxy modification (0.5–10 wt %), the tensile strengths and Young’s moduli of the epoxy-modified pine/PLA composites increased by up to 20 and 82%, respectively, as compared to that of neat PLA. The epoxy-modified pine/PLA composites, with an optimum epoxy modification (1.0 wt %), had fewer voids on the fracture surface as compared with pine/PLA composites without the modification of pine fibers via epoxy. Results confirmed that epoxy partially penetrated the pore/hollow inner structures of pine fibers and improved the fiber/matrix interfacial adhesion. Epoxy modification is found to be a simple and effective technique to improve the properties of biocomposites.

Insight into roles of different types of additives on mechanical and crystalline properties of polylactic acid

“…They found the tensile strengths and Young's moduli of the epoxy-modified pine/PLA (0.5-10 wt%) composites increased by up to 20% and 82% respectively, as compared to those of neat PLA, which is attributed to epoxy partially immersing into the inner structures of pine fibers and thus improved the interfacial adhesion. 31 Sui et al prepared ternary PLA-based composites by a reactive and high-shear extrusion, in order to control well the phase morphologies and improve the properties. It is reported that the suitable dispersed phase size and appropriate interfacial adhesion led to an obvious enhancement of impact toughness, primarily benefited from the combined effect of reactive and high-shear extrusion.…”

Tailoring of advanced poly(lactic acid)‐based materials: A review

“…Processes of PLA melt blending and molding require high operating temperatures above the polymer melting point (up to 200°C) and/or high pressures 16,19,22,24,39,56–68 . After being melted, PLA is shaped into the desired form by molding (with or without a mechanical press) and cooled down to stabilize its dimensions 23 …”

“…Blending of PLA with other polymers has been suggested for creation of materials with tailored mechanical, thermal, viscoelastic, and biodegradation properties 56,74,75,78,82,86,117,120,122,128–130,132,172,185 . Milovanovic et al 117 reported that the addition of 5 wt% PCL to PLA 2 film favored sorption of scCO 2 , decreased degradation temperature from 379.3 to 374.1°C, and T m from 161 to 154°C.…”

Water-Induced Breaking of Interfacial Cohesiveness in a Poly(lactic acid)/Miscanthus Fibers Biocomposite

“…In this context, material scientists look for solutions that keep the functionalities at use and have a minimum environmental impact [ 1 ]. Biocomposites properties have thus been investigated with a large variety of matrices and vegetal fiber reinforcements [ 2 , 3 ]. Poly lactic acid (PLA) notably is one of the main actors in biomaterials industrialization, targeting the packaging market.…”